Omaha, Neb. — The U.S. Army Corps of Engineers (Corps) Missouri River Basin Water Management Division will begin using the Oahe Dam outlet tunnels to supplement powerhouse releases of stored flood water starting Wednesday, Sept. 24.
“Maintenance being done on the powerhouse at Oahe Dam is limiting release capacity, so utilizing the outlet tunnels will help continue moving water through the Missouri River Mainstem Reservoir System,” said Jody Farhat, chief of the Missouri River Basin Water Management Office. “The total release from Oahe will be similar to that experienced in recent weeks, but it now will be split between the powerhouse and the outlet tunnels.” At the peak of the runoff season this year, more than 5 million acre feet (MAF) of flood water was stored in the reservoir system requiring evacuation prior to next year.
The combined releases from the Oahe powerhouse and outlet tunnels will be in the range of 38,000 to 42,000 cubic feet per second (cfs), which is the same as in recent weeks, and will result in similar downstream stages. “As always, we will monitor conditions to determine whether any adjustments are necessary,” assures Farhat. “Releases from the outlet tunnel will be discontinued once powerhouse releases are able to return to desired levels.”
Oahe reservoir peaked earlier this month at elevation 1615.3 feet and is now down to 1613.7 feet. “The reservoir still needs to be lowered another 6.2 feet by the beginning of March next year. Lower energy demand, unit maintenance, and transmission restrictions have limited releases through the Oahe powerhouse in recent days and necessitated the supplemental releases,” explains Farhat. The Oahe releases, which are passed directly through Big Bend Dam, provide downstream support to Fort Randall reservoir, which is currently near elevation 1352.4 feet. Fort Randall reservoir is normally drawn down to 1337.5 feet in the fall; however the drawdown is ahead of schedule due to the limited powerhouse releases from Oahe. “The supplemental releases from the Oahe outlet tunnels will help maintain the scheduled Fort Randall reservoir drawdown,” states Farhat.
Release no. 20140923-001